Hippos & Silicon: An Unexpected Life Giver

Along with being one of the most well-known animals of the African savannah, Hippos are also a vital part of the regions exosystem.

Hippos are responsible for most of the silicon that exists in their water habitat.

The semi-aquatic mammals have an exciting lifestyle. While they spend their nights on land eating tons of fresh grass in the Savannahs, the daytime is often spent basking in rivers or lakes.

Aside from keeping them far from the reach of enemies, this practice also protects the hippos from the sun’s glare. But it also has one more unintended effect – maintaining the food web in their lake or river.

Hippo’s digestion tends to get active during their daytime skinny-dipping. And as a result, the animals dump an enormous amount of minerals into the water.

According to a biologist from the University of Antwerp and the first author of the study, Jonas Schoelynck, not only is this a good thing, but it also makes hippos a unique and essential grazer in the savannah.

“The nutrients in the excrements of most grazers largely end up back in the savannah again, where the plants reabsorb them. This is not the case with hippos: they act as a kind of nutrient pump from the land to rivers and lakes.”

Now Schoelynck and his team have published a study which shows that this pumping action is essential for life in water.

How Hippos Maintain Nature’s Silicon Balance

The grass that hippos eat contains silicon, which is absorbed from the groundwater.

In the study, researcher Patrick Frings from the Geochemistry of the Earth’s Surface Section of the GFZ collected samples of the grass, water, as well as hippo excrement. His goal was simple; to analyze the isotopic composition of silicon present in all three samples.

“The isotope analysis enabled us to reconstruct the transport path of the silicon,”explains Frings.

Based on the analysis, the researchers noted that hippos are responsible for more than half of the silicon in the Mara River.

The semi-aquatic mammals in the investigated part of southwest Kenya consume a total of 800 Kilograms of silicon per day through the plants. Half of this silicon mass ends up in the water when the hippos dump their feces.

According to estimates, this contribution influences more than 76 percent of the total silicon that’s transported along the Mara River. That means that as far as the biogeochemical silicon cycle of certain areas is concerned, Hippos may be the single most crucial factor.

“So far, it has not been assumed that grazing wild animals could have such an influence on the transport of silicon from land to lakes. This process is crucial for the entire land-water ecosystem. In the past, however, it has simply been overlooked.”

A World Without Hippos

Individual organisms such as diatoms depend on silicon to survive. Since such unicellular live in water and produce oxygen, they form the foundation of the food chain in various water ecosystem.

That means an absence of silicon would collapse the algae population; and with it, the entire food web in the lake or river.

“If the diatoms do not get enough silicon, they are replaced by pest algae, which have all sorts of unpleasant consequences, such as a lack of oxygen and the associated death of fish,”said Schoelynck.